Vapor compressor

ABSTRACT

THE PISTON IN A ROTARY-TYPE COMPRESSOR MAKES A SLIP FIT ON A ROTATABLE ECCENTRIC RAM, AND IS PREVENTED FROM ROTATING WITH RESPECT TO THE COMPRESSION CYLINDER BY A SLIDABLE VANE WHICH FITS IN A SLOT IN THE PISTON AND A RECESS IN THE CYLINDER. A SECOND SLIDABLE VANE FITS IN A RECESS ON THE OPPOSITITE SIDE OF THE CYLINDER AND BEARS AGAINST THE SURFACE OF THE PISTON TO DIVIDE THE CYLINDER INTO TWO COMPRESSION CHAMBERS.

Jan. 12, 1971 J. o. Pbmsous 3,554,676

VAPOR COMPRESSOR Filed Feb. 5', 1969 s Sheets-Sheet 2 J. o. PORTEOUS VAPOR COMPRESSOR Janilz; 1971 I 3 Sheets-Sheet 3 Filed Feb s, '1969" United States Patent Office 3,554,676 VAPOR COMPRESSOR John O. Porteous, Pasadena, Calif., assignor to Loren A. Porteous Filed Feb. 5, 1969, Ser. No. 796,840 Int. Cl. F04c 17/02 US. Cl. 418-61 4 Claims ABSTRACT OF THE DISCLOSURE The piston in a rotary-type compressor makes a slip fit on a rotatable eccentric cam, and is prevented from rotating with respect to the compression cylinder 'by a slidable vane which fits in a slot in the piston and a recess in the cylinder. A second slidable vane fits in a recess on the opposite side of the cylinder and bears against the surface of the piston to divide the cylinder into two compression chambers.

BACKGROUND OF THE INVENTION This invention relates to rotary compressors and more particularly to high pressure and high temperature refrigerant vapor compressors.

Rotary compressors are particularly useful in refrigerating apparatus. In many of these devices, an impeller is disposed within a cylindrical housing to draw low pressure refrigerant vapor into a compression chamber, compress the vapor, and discharge it through an exhaust port. Movable vanes ordinarily separate the cylinder into two or more compression chambers. Rotary compressors having a variety of intake and exhaust systems and varying numbers of vanes are useful because they are generally capable of smooth and trouble-free operation.

Rotary compressors for refrigeration apparatus are subjected to considerably higher demands than simple rotary compressors. For example, refrigerant compressors must admit incoming cold vapor at low pressure and compress it to a high pressure and temperature. Conventional refrigerant compressors have been unduly complex when attempting to meet these requirements. Consequently, initial costs and maintenance have been high, and operation has been less than satisfactory.

Attempts have been made to design rotary piston compressors with vanes which bear against the working surfaces of the piston to separate the cylinder into compression chambers. During operation of these compressors, it is difiicult to maintain the proper spring pressure to be exerted by each vane on the Working surface of the piston. At high speeds, the piston tends to become unbalanced, causing substantial vibration and excessive bearing wear. Furthermore, the pumping efficiency of these compressors is impaired because portions of the Working surface of the piston are engaged by more than one vane. Each vane causes the surface of the piston to wear differently, and as a result, the effectiveness of the seal between a particular vane and the piston surface is adversely affected.

The pump of this invention has two opposing vanes which bear against opposite sides of the piston. During operation, the vanes cooperate to exert equal and opposite spring pressures on the working surface of the :piston through the center-line of the piston. This pump is of improved efficiency because it has better balance and less bearing wear, particularly at high speeds. In addition, the rotation of the piston is limited to an oscillatory movement, which confines each part of the working surface of the piston to a restricted area of the cylinder. Thus, the contacting area of the piston wears evenly against the vanes and the cylinder wall to provide a more effective seal.

3,554,676 Patented Jan. 12, 1971 SUMMARY OF THE INVENTION The vapor compressor of this invention has a piston disposed within an oversized cylindrical housing between a high pressure chamber and a low pressure chamber. The piston makes a slip fit over a cam eccentrically mounted on a drive shaft so that rotary movement of the shaft imparts planetary motion to the piston. The piston makes contact with the cylinder along a line that travels around the cylinder with the rotation of the cam. The piston is prevented from rotating with respect to the cylinder by a vane which fits in a slot in the piston periphery and in a recess in the cylinder. Preferably, the slot-engaging end of the vane has a rounded edge which fits into a matching arcuate slot running the length of the piston. During planetary movement of the piston, the vane prevents the piston from rotating, thereby imparting an oscillatory motion to the piston.

A second vane, spaced 180 from the slot-engaging vane, slides in another recess of the cylinder, and has a sealing member, or shoe, which conforms to and rides on the peripheral working surface of the piston. The shoe rides back and forth over a limited area of the piston in response to its oscillatory and planetary movement. Since the piston is confined to a limited oscillatory movement, it wears evenly against the shoe and the cylinder wall to provide an efiicient seal.

The slot-engaging vane co-acts with the sliding vane to divide the space between the piston and the cylinder into separate compression chambers. Each chamber has an inlet and outlet which communicate with the low and high pressure chambers respectively. The inlet and outlet are alternately covered and exposed during planetary movement of the piston to admit, compress, and exhaust the refrigerant vapor. A check valve in the outlet prevents backflow after the completion of the compression stroke.

The sliding vane preferably has an arcuate recess along its inner edge. In transverse cross-section, the recess defines an arc of a circle slightly in excess of 180. The shoe is disposed within the recess without the need for pins or other restraining members to hold it in the second vane. That is, the slightly overlapping edges of the inner end of the second vane firmly hold the shoe within the arcuate recess. The shoe itself projects from the recess and conforms to the peripheral surface of the piston as it moves within the cylinder. The shoe is free to rotate within the arcuate recess of the vane, and thereby cooperates with the slot-engaging vane to allow precise oscillation of the piston in a smoothly functioning manner and with a minimum of friction.

The drive shaft is preferably driven by a motor adjacent the low pressure chamber of the compressor. Refrigerant, at about F., is preferably drawn back over the motor from the chamber to cool the motor during operation; alternately, water or other suitable liquid can be used for cooling. A centrifugal-type oil pump is preferably disposed below the motor With lines running from the pump to drive shaft bearings and other friction areas of the compressor.

The invention will be more fully understood from the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary elevational sectional view of a refrigerant vapor compressor of this invention;

FIG. 2 is a view taken on line 22 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 showing a successive stage of operation of the compressor;

FIG. 4 is a fragmentary sectional view, partially broken away, similar to FIGS. 2 and 3, and showing another stage of operation of the compressor;

FIG. is a view taken on line 5--5 of FIG. 1; and FIG. 6 is a view taken on line 66 of FIG. 5 of the exhaust port check valve of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an upright cylindrical housing 10 contains an annular high pressure chamber 12 at its upper end, a compression cylinder 13, and an annular low pressure chamber 14 immediately below the cylinder. Refrigerant vapor enters the low pressure chamber through an inlet 16 and, after being compressed within the cylinder, passes through the high pressure chamber and out a discharge outlet 17. The discharge outlet is controlled by a standard refrigerating shut off valve (not shown) connected to the high pressure side of a refrigerating system (not shown).

A hollow piston 18 is disposed within compression cylinder 13. A cam 19 is journaled in bearings 20 and 21 and fitted into the hollow interior of the piston. The cam is integral with and eccentric of the axis of a vertical drive shaft 22. The drive shaft constitutes the armature shaft of an electric motor 23 disposed within the lower portion of compressor housing 10 inside a sealed casing 23a. The motor includes a stator 23b which is held in place by a press fit in housing 10. The stator is provided with a series of windings 23c about its periphery. A rotor 23d is fitted onto drive shaft 22 which is journaled in a sleeve bearing 23c and a thrust bearing 23 The bearings are mounted in a bearing support 23g which forms a part of casing 23a. Rotation of the drive shaft causes the cam and the piston to move in a planetary fashion. The piston is also capable of rotating independently of the cam. A portion of housing 10 adjacent motor 23 is reduced in diameter and enclosed by a cylindrical casing 24 to define an annular space 24a. Casing 24 has an inlet opening 25a and an outlet opening 25b adapted for connection to a water circulating system (not shown) or a refrigerant circulating system (not shown) for cooling the motor during operation of the compressor.

The drive shaft is journaled in main bearings 26 and 27 supported by a stationary head portion 28 of motor 23. The head constitutes the housing for low pressure chamber 14. The opposite end 29 of drive shaft 22 is reduced in diameter and journaled in a sleeve bearing 30 in a head portion 31 of the compressor. The reduced end 29 of the shaft co-acts with lower sleeve bearing 23c in motor 23 to provide for rotation of the drive shaft about a fixed axis. Piston 18 is a cylindrical member having a working fit between the heads 28 and 31 and defining peripheral working surfaces 33 and 34.

Refrigerant vapor passes from the low pressure chamber 14 into the cylinder through left and right (as viewed in FIG. 2) intake ports 35 and 36. FIG. 2 shows the lower end wall of piston 18 covering the right intake port and exposing the left intake port. The left side 35a of compression cylinder 13 draws low pressure vapor from low pressure chamber through intake port 35. Left and right (FIG. 5) exhaust ports 37 and 38 extend through head 31 and are similarly covered and exposed by the upper end wall of the piston. The exhaust ports are controlled by spring-loaded check valves secured to the upper surface of head 31 by a pair of cap screws 39. FIG. 6 shows an outwardly opening check valve 40 urged by a tension spring 41 to close exhaust port 37. When exhaust port 37 is opened, the angular displacement of check valve 40 is limited by an arcuate stop block 42 secured to the top of spring 41. An annular groove 43 around the exhaust port improves the venting and sealing of valve 40. A recess 44 in head 31 is disposed below the check valve and adjacent exhaust port 37 to provide a receptacle for debris such as dirt or grease that might interfere with the efficient operation of the valve.

In operation, the electric motor rotates drive shaft 22. The lower end of the drive shaft passes through a centrifugal oil pump 45 (FIG. 1) disposed below the motor. The pump has a plurality of impeller vanes 46 secured to the lower part of the drive shaft. Rotation of the vanes pumps oil from a reservoir 47 in the pump upward through an axial passage 48 in the drive shaft. A series of lateral passages 48a in the shaft deliver oil from the axial passage to the shaft and piston bearings and to working surfaces 33 and 34 of the piston.

FIG. 2 shows the position of the piston after completing a compression stroke. An arcuate slot 49 runs the length of the piston. A slot-engaging vane 50 and a sliding vane 51 are slidably mounted in recesses 50a and 51a of the cylinder walls and are coextensive in length with the piston. The vanes have pockets 52 and 53 to receive coil compression springs 54 and 55 which urge the vanes toward the working surface of the piston. The inner end of slotengaging vane 50 has a rounded edge which fits into the arcuate slot 49. The sliding vane 51 is positioned directly opposite the slot-engaging vane, and has an arcuate recess 56 along its inner edge. The recess defines a circular are slightly in excess of 180. A sealing member or shoe 58, having an edge coextensive with the length of the piston and conforming to the periphery of the piston, is movably seated in the recess. The shoe rotates with the recess in response to oscillation of the piston during its planetary movement, but is restrained within the recess by the slightly overlapping edges of the vane. The shoe rides on the peripheral working surface of the piston and distributes the frictional load resulting from the spring pressure over a relatively large surface area. During its eccentric movement within the cylinder, the piston rocks back and forth on the rounded edge of the slot-engaging vane while the sliding vane allows the opposite end of the piston to move freely. This causes the piston to oscillate during its planetary movement within the cylinder. The slot-engaging vane and sliding vane cooperate to define adjacent compression chambers 35a and 36a and to confine high pressure refrigerant vapor against leakage from the chambers.

Shoe 58 is movably disposed in the arcuate recess of the sliding vane so that it remains in precise contact with the surface of the piston regardless of its oscillatory position. During high speed operation of the pump, compression springs 54 and 55 cooperate with the vanes to continuously produce equal opposite spring pressure on the surface of the piston. Thus, piston vibration and main bearing wear are minimized. The shoe oscillates within the recess in response to movement of the piston, and makes sliding contact with a limited area of the surface of the piston. Consequently, that limited area of the working surface of the piston and the shoe wear evenly, thereby assuring an efficient and smoothly functioning seal.

The reduced end 29 of the drive shaft which passes through head 31 has a counterweight 68 affixed thereto to compensate for the eccentrically disposed mass of the piston 18.

In operation of the compressor, the inlet opening 16 and outlet opening 17 are connected to the low and high pressure sides, respectively, of a refrigerating system (not shown) for compressing and circulating a refrigerant vapor through the compressor. Heat is removed from the refrigerant exteriorly of the compressor so that the latter operates only on a vaporous fiuid.

The cycle of operation for compression chambers 35a and 36a is identical and occurs successively at each 180 of travel of the drive shaft which rotates in a counterclockwise direction as viewed in FIGS. 2, 3 and 4. Consequently, a description of the operation of compression chamber 36a will suffice for both. When the piston is in the position shown in FIG. 2, intake port 36 is closed by the lower end wall of the piston. As the piston is advanced through approximately of rotation by the drive shaft to the position shown in FIG. 3, a partial vacuum is created in compression chamber 36a as the working surface of the piston moves away from the cylinder wall. Intake port 36 is opened by the lower end wall of the.

piston to admit refrigerant vapor from low pressure chamber 14. As the shaft continues to rotate the piston from the position shown in FIG. 3, intake port 36 is closed, and exhaust port 38 is opened by the upper end wall of the piston. When the piston reaches the position shown in FIG. 4, intake port 36 is substantially closed and exhaust port 38 reaches its maximum opening. As the drive shaft completes one revolution, the refrigerant vapor in compression chamber 36a is compressed by the piston and forced through exhaust port 38 past check valve 40 and into high pressure chamber 12. During the operating cycle the compression chambers 35a and 3611 are sealed fluid-tight by slot-engaging vane 50 and shoe 58 to confine the high pressure refrigrant vapor against leakage.

Although the embodiment described above includes two vanes and two working chambers, a compressor built in accordance with this invention can use only one vane or more than two vanes. For example, the sliding vane with the shoe can be omitted, and the inlet and outlet ports can be located adjacent and on opposite sides of the slot-engaging vane. However, in this embodiment the piston tends to become unbalanced at high speeds because there is no opposing spring pressure on the opposite side of the piston to cooperate with the pressure exerted by the slot-engaging vane. Furthermore, no vane is present to counteract the pressure on the main bearings, and consequently, bearing wear is increased.

What is claimed is:

1. A vapor compressor comprising a cylinder disposed between a high pressure chamber and a low pressure chamber, a rotatable cam disposed within the cylinder, a piston slip-fitted over the cam and disposed within the cylinder, the piston being of smaller diameter than the cylinder and making contact with a substantial portion of the cylinder along a line that travels around the cylinder with the rotation of the cam, a first recess disposed in the cylinder and opening toward the piston, a slot disposed in the piston and opening toward the first recess, a first slidable vane disposed in the first recess and spring-urged into engagement with the piston slot to restrict the rotation of the piston within the cylinder, a second recess disposed in the cylinder opposite the first recess and opening toward the piston, a second slidable vane disposed in the second recess and spring-urged into engagement with the piston to divide the cylinder into two compression chambers, each compression chamber having an inlet and an outlet communicating with the low and high pressure chambers respectively, means for rotating the cam to cause the piston to oscillate within the cylinder and force vapor from each inlet toward its respective outlet, and a check valve in each outlet.

2. A compressor according to claim 1 in which the piston slot is arcuate and the end of the first vane has a matching curved surface.

3. The compressor of claim 1 wherein a recess is disposed in the piston-engaging edge of the second vane, and a sealing member is disposed within the recess to ride on the periphery of the piston and seal the compression chambers.

4. The compressor of claim 3 wherein the recess of the second vane is arcuate and defines an arc in excess of such that the sealing member is firmly held by the sides of the vane and is movable in the recess in response to movement of the piston.

References Cited UNITED STATES PATENTS 910,175 l/l909 Cole 230-147 2,015,307 9/1935 Hand 9156 2,635,553 4/1953 Gordinier l03132 3,259,306 7/1966 Porteous 230147 MARK NEWMAN, Primary Examiner W. J. GOODLIN, Assistant Examiner US. Cl. X.R. 41862, 63 

